i. Field of the Invention
This invention relates to bipolar electrodes. More particularly, it relates to modular bipolar electrode assemblies specially adapted for use in a bipolar electrolytic cell, and to the bipolar electrolytic cell so provided.
II. Description of the Prior Art
It is known that electrolytic cells for the production of metal chlorates using carbon electrodes have certain disadvantages. Monopolar cells inherently have many power connection and electrolytic branches and thus suffer from high electrode stub losses, high voltage drops and high power loss. Furthermore, many units are required in commercial production, and much larger building spaces are required.
Bipolar electrolytic cells designed to avoid many of the above difficulties have been mainly successful, but have brought about one major problem. Such cells have traditionally been designed to operate with a gas phase above the level of the liquid and below the cell cover. The electrical connections to the electrode (generally a graphite electrode) is situated in this gas phase and accordingly, the danger of sparks occuring with the resulting explosion is always present.
A major improvement is these types of bipolar electrolytic cells was provided in Canadian Pat. No. 714,778 issued Aug. 30, 1966 to G. O. Westerlund. In that patent, an electrolytic metal chlorate cell was provided which included a cell box provided with a closure. A plurality of bipolar electrodes were positioned in the cell box and were constructed and arranged to conduct electric current through the box and through a circulating electrolyte. Inlet means were provided to means associated with the closure to provide inlet to the cell box and a distribution means for the electrolyte inlet. Means were provided for inhibiting the accumulation of gaseous products of electrolysis in the zone adjacent the closure. Means were provided for circulating within the cell box by combined forced external pumping means and internal pumping action due to the construction and arrangement of the bipolar electrodes and the rising gaseous products of electrolysis. Means were also provided, external of the closure by associated therewith, for providing an outlet for the electrolyte and the gaseous products of electrolysis and for partially or completely separating the electrolyte from the gaseous products of electrolysis.
There have been further developments both in the design of electrolytic cells and in the design of the electrodes disposed therein. One such electrolytic cell is taught in U.S. Pat. No. 3,219,563 issued Nov. 23, 1965 to J. H. Collins et al. This patent provides a multi-electrolytic cell comprising a plurality of individual cell units made up of a cathode and an anode and an inter-electrode electrolysis space therebetween. The cells are arranged so that a partition (comprising an inert titanium sheet) carries the anode of one cell and the cathode of the next cell. Such inert titanium sheet not only separates the anode of one unit electrolytic cell from the cathode of an adjacent unit but is in electrical conducting relationship with respect both to the anode and the cathode carried thereby. The anode of one cell comprises a layer of a platinum metal on one side of the titanium metal portition, and the cathode of the adjacent cell comprises of a layer of a platinum metal or iron or steel on the other side of the titanium metal partition.
Electrolytic cells generally have included complex construction in order to facilitate the mounting of electrodes. Another new development in cell design is shown in Canadian Pat. No. 914,610 issued to G. O. Westerlund for multi-monopolar electrolytic cell assembly. Although this design has a proven efficient performance, the construction is not one which can readily be carried out in the field. This is because the modular cell assembly comprises a plurality of electrode plates which must be carefully fitted when assembling the multi-unit cell in order to avoid electrical short circuiting between adjacent cell modules. Cells designed for operation under low voltage conditions by having close spacing between electrodes are thus not readily maintained or constructed in the field. This disadvantage also applies to most other high efficiency electrolytic cells.
The above-identified Canadian Pat. No. 914,610 also provides novel metal electrode constructions for electrolytic cells. However, according to that patent, the combined electrolyzer reactor employed an electrode arrangement where all anodes were welded to a first carrier plate. A second carrier plate was provided having cathode steel plates. In the electrolyzer the cathodes of the second carrier plate were fitted between the anodes of the first carrier plate. This required, on the average, 8 hours for fitting within the cell, in order to avoid the presence of any electrical short circuits.